// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_
#define MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_

#include <windows.h>
#include <mmsystem.h>
#include <mmreg.h>
#include <stddef.h>
#include <stdint.h>

#include <memory>

#include "base/macros.h"
#include "base/synchronization/lock.h"
#include "base/win/scoped_handle.h"
#include "media/audio/audio_io.h"
#include "media/base/audio_parameters.h"

namespace media {

class AudioManagerWin;

// Implements PCM audio output support for Windows using the WaveXXX API.
// While not as nice as the DirectSound-based API, it should work in all target
// operating systems regardless or DirectX version installed. It is known that
// in some machines WaveXXX based audio is better while in others DirectSound
// is better.
//
// Important: the OnXXXX functions in AudioSourceCallback are called by more
// than one thread so it is important to have some form of synchronization if
// you are keeping state in it.
class PCMWaveOutAudioOutputStream : public AudioOutputStream {
public:
    // The ctor takes all the usual parameters, plus |manager| which is the the
    // audio manager who is creating this object and |device_id| which is provided
    // by the operating system.
    PCMWaveOutAudioOutputStream(AudioManagerWin* manager,
        const AudioParameters& params,
        int num_buffers,
        UINT device_id);
    ~PCMWaveOutAudioOutputStream() override;

    // Implementation of AudioOutputStream.
    bool Open() override;
    void Close() override;
    void Start(AudioSourceCallback* callback) override;
    void Stop() override;
    void SetVolume(double volume) override;
    void GetVolume(double* volume) override;

    // Sends a buffer to the audio driver for playback.
    void QueueNextPacket(WAVEHDR* buffer);

private:
    enum State {
        PCMA_BRAND_NEW, // Initial state.
        PCMA_READY, // Device obtained and ready to play.
        PCMA_PLAYING, // Playing audio.
        PCMA_STOPPING, // Audio is stopping, do not "feed" data to Windows.
        PCMA_CLOSED // Device has been released.
    };

    // Returns pointer to the n-th buffer.
    inline WAVEHDR* GetBuffer(int n) const;

    // Size of one buffer in bytes, rounded up if necessary.
    inline size_t BufferSize() const;

    // Windows calls us back asking for more data when buffer_event_ signalled.
    // See MSDN for help on RegisterWaitForSingleObject() and waveOutOpen().
    static void NTAPI BufferCallback(PVOID lpParameter, BOOLEAN timer_fired);

    // If windows reports an error this function handles it and passes it to
    // the attached AudioSourceCallback::OnError().
    void HandleError(MMRESULT error);

    // Allocates and prepares the memory that will be used for playback.
    void SetupBuffers();

    // Deallocates the memory allocated in SetupBuffers.
    void FreeBuffers();

    // Reader beware. Visual C has stronger guarantees on volatile vars than
    // most people expect. In fact, it has release semantics on write and
    // acquire semantics on reads. See the msdn documentation.
    volatile State state_;

    // The audio manager that created this output stream. We notify it when
    // we close so it can release its own resources.
    AudioManagerWin* manager_;

    // We use the callback mostly to periodically request more audio data.
    AudioSourceCallback* callback_;

    // The number of buffers of size |buffer_size_| each to use.
    const int num_buffers_;

    // The size in bytes of each audio buffer, we usually have two of these.
    uint32_t buffer_size_;

    // Volume level from 0 to 1.
    float volume_;

    // Channels from 0 to 8.
    const int channels_;

    // Number of bytes yet to be played in the hardware buffer.
    uint32_t pending_bytes_;

    // The id assigned by the operating system to the selected wave output
    // hardware device. Usually this is just -1 which means 'default device'.
    UINT device_id_;

    // Windows native structure to encode the format parameters.
    WAVEFORMATPCMEX format_;

    // Handle to the instance of the wave device.
    HWAVEOUT waveout_;

    // Handle to the buffer event.
    base::win::ScopedHandle buffer_event_;

    // Handle returned by RegisterWaitForSingleObject().
    HANDLE waiting_handle_;

    // Pointer to the allocated audio buffers, we allocate all buffers in one big
    // chunk. This object owns them.
    std::unique_ptr<char[]> buffers_;

    // Lock used to avoid the conflict when callbacks are called simultaneously.
    base::Lock lock_;

    // Container for retrieving data from AudioSourceCallback::OnMoreData().
    std::unique_ptr<AudioBus> audio_bus_;

    DISALLOW_COPY_AND_ASSIGN(PCMWaveOutAudioOutputStream);
};

} // namespace media

#endif // MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_
